Yes, you can save and come back when you are ready to complete your tax return. TurboTax Online automatically saves your work as you go through the interview. When you sign out, we'll make sure to save everything before we log you out. Just make sure that when you return to complete your return that you sign in with the same username and password that you used to start this return. 

Please see the following TurboTax FAQ for more information on saving your return:
 

https://ttlc.intuit.com/replies/3301211

Yes, you can. TurboTax will automatically save your information but you can also click Sign out at the bottom left-hand corner of the TurboTax screen. Just remember when you come back to use the same user id and password as you used to start your return that way you will pick up right where you left off.